Let us conclude this preliminary section with a reminder on (many-sorted) essentially algebraic categories [1]}, [2]} (or in other words locally presentable categories [3]}) as we will need them to prove Theorem REF . They are described by essentially algebraic theories, i.e., quintuples
\(\Gamma =(S,\Sigma ,E,\Sigma _t,\mathsf {Def})\) 
